Catalytic preparation of carboxylic acid esters from olefins,alcohols and carbon monoxide in the presence of an alkyl ether and an activator amount of water

ABSTRACT

A PROCESS IS DESCRIBED FOR PREPARING CARBOXYLIC ACID ESTERS FROM OLEFINS, ALCOHOLS AND CARBON MONOXIDE USING A COMBINATION OF TIN OR GERMANIUM SALT; A PLATINUM SALT AS THE CATALYST, AN ETHER AND AN ACTIVATOR AMOUNT OF WATER. OLEFINS HAVING FROM 8 TO ABOUT 24 CARBON ATOMS ARE PREFERRED REACTANTS. ALKYL ETHERS HAVING UP TO 16 CARBON ATOMS ARE USEFUL. THE REACTION RATE IS UNEXPECTEDLY IMPROVED BY THE COMBINATION OF ALKYLETHER AND ACTIVATOR.

United States Patent Office 3,661,948 Patented May 9, 1972 US. Cl.260410.9 R 33 Claims ABSTRACT OF THE DISCLOSURE A process is describedfor preparing carboxylic acid esters from olefins, alcohols and carbonmonoxide using a combination of tin or germanium salt; a platinum saltas the catalyst, an ether and an activator amount of water.

Olefins having from 8 to about 24 carbon atoms are preferred reactants.Alkyl ethers having up to 16 carbon atoms are useful.

The reaction rate is unexpectedly improved by the combination ofalkylether and activator.

CROSS REFERENCE TO RELATED APPLICATION This application is acontinuation-in-part of Ser. No. 671,110, filed Sept. 27, 967, nowabandoned.

BACKGROUND OF THE INVENTION This invention is directed to an improvedprocess for preparing carboxylic acid esters from olefins, carbonmonoxide and alcohols.

The reaction of primary alcohols with olefins and carbon monoxide toproduce esters is well known. There are a number of US. patentsdescribing the use of various catalysts for this reaction, see forexample, US. 2,542,767, US. 2,526,742, US. 2,557,256. An especiallyuseful catalyst system is described in US. 2,876,254. The processtherein described is directed to the reaction of olefins having up tosix carbon atoms with carbon monoxide and an alcohol using as a catalysta combination of a tin or germanium salt with a Group VIII metal salt.When higher molecular weight olefins such as dodecene are used in thisprocess, the yield of ester product is low and the rate of reaction ispoor.

It has been discovered that the rate of carboxylating higher molecularweight olefins using a catalyst of US. 2,876,254 is significantlyincreased by carrying the reaction out in the presence of ethers and asmall amount of water as an activator.

SUMMARY OF THE INVENTION A process for preparing carboxylic acid esterswhich comprises reacting an olefin having from about 2 to about 32carbon atoms with carbon monoxide and an alcohol using a catalyst whichis a combination of a salt of tin or germanium with a platinum salt inthe presence of an alkyl ether and an activator amount of water.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of this inventionis a process for preparing carboxylic acid esters which comprisesreacting a C2-C32 olefin characterized by (1) having at least onea-carbon-to-carbon double bond and (2) having a hydrogen on the 2 carbonatom of said a double bond with carbon monoxide and a -0 alcohol in thepresence of a catalyst which is a combination of an alcohol soluble saltof a metal selected from the class consisting of tin and germanium withplatinum salts, an alkyl ether and an activator amount of H 0. Apreferred embodiment is the process described above in which thecatalyst is a combination of (a) a tin or germanium halide with platinumhalide salt or (b) a tin or germanium halide with alkali metal salt of ahaloplatinum acid or (c) stannous chloride dihydrate and K PtCl K PtCland the like. C -C monohydroxy alkanols are preferred reactant alcohols.Alpha monoolefins are preferred olefins. Alkyl ethers having up to about16 carbon atoms are preferred. A most preferred process is the catalyticprocess described above wherein methanol is the reactant alcohol and1,2-dimethoxyethane is the ether.

Organic compounds which are useful reactants in the practice of thisinvention are olefins (1) having at least one alpha carbon-to-carbondouble bond and (2) a hydrogen atom on the 2 carbon atoms of said adouble bond. These olefins include mono unsaturates, that is, compoundshaving one a carbon-to-carbon double bond as well as polyunsaturates,that is, compounds having two or more carbon-to-carbon double bonds.Useful olefins may contain other functional groups such as hydroxy,halo, carboxy, nitro and the like. Examples of useful unsaturatedorganic compounds are 3-chlorooctene-l, 9-hydroxytetradecene-l, and thelike. Preferred olefins are the hydrocarbon olefins. Examples ofpreferred olefins are octene-l, pentadecene-l, tetraisobutylene,cyclooctene, cyclooctadiene-l,5, dodecene-l, eicosene-l, nonene-l,octadecene-l and the like. Most preferred olefins are the acrylic eolefins. Examples of preferred olefins are tetracosene- 1,octadecadiene-1,3, undecadiene-1,4, and the like. Especially preferredhydrocarbon olefins are the a-IllOIlOOlC- fins, that is, hydrocarbonshaving only one carbon-to-carbon double bond in the 1,2 position in themolecule. Examples of suitable a-monoolefins are ethylene,4-methylpentene-l, butene-l, 3-methylbutene-1, octene-l, nonene- 1,decene-l, tetradecene-l, dodecene-l, S-ethylhexene-l, pentadecene-l,heptadecene-l, eicosene-l, and the like.

Commercial mixtures of olefins are also quite useful. These commercialmixtures are generally a mixture of various homologous olefins such as CC C olefins; C C7, C9, C11 olefins; C12, C14, C16 olefins; C12, C14olefins; 13 15 17 Olefins; 11 12 13 14 15 Olefins; 13 20, 22 Olefins; 1415 Olefins; 12 14 C16, C18 20 C22, C C26, C olefins, and the like. Thesemixed olefins are synthesized for example by the Ziegler catalyzedpolymerization of low molecular weight olefins such as ethylene orpropylene; or by the dehydrogenation of suitable paratfins. The mixedolefins thus obtained might also contain minor amounts of othernon-homologous olefins and non-olefin components. In any case, the mixedproduct obtained from such a commercial synthesis need not be separatedinto the individual components to be useful. Mixtures of even carbonnumbered predominantly a olefins in the C C range having an averagemolecular weight of 0 ,0 are useful; C1048 range mixtures areparticularly useful. Such mixtures containing C to C predominantlytit-olefins are especially useful. By predominantly I mean that over 60%of the olefins are alpha.

Alcohols which are useful reactants include both aryl as well as alkylhydroxy compounds. Examples of suitable aryl hydroxy compounds arebenzyl alcohol, phenol, C to C alkyl phenols, and the like. Thepreferred alcohols are the alkyl hydroxy compounds having from 1 toabout 10 carbon atoms wherein the alkyl group is composed solely ofcarbon and hydrogen. The term hydrocarbyl alkanols is used to describethese preferred alcohols. These hydrocarbyl alkanols include cyclicalcohols such as cyclohexanol, cyclopentanol and the like, as well asprimary, secondary and tertiary alcohols such as Z-decanol,tert-butanol, 2-ethylhexanol-1 and the like.

The most preferred alcohols are the acyclic hydrocarbyl mouohydroxyprimary alkanols having from 1 to about carbon atoms such as ethanol,pentanol-l, butanol and the like. Methanol is an especially preferredalcohol.

The catalysts which are used in effecting the reaction are in general acombination of alcohol soluble salts of tin or germanium with platinumsalts. Preferred salts are halides wherein the halogen has an atomicnumber of at least 17. The chlorides are especially preferred. Specificexamples of suitable salts of tin and germanium are stannous and stannicchlorides, bromides and iodides, germanium diand tetrachlorides andgermanium tetrabromides, tetraiodides and tetrafluorides, stannous andstannic sulfates and the like and their hydrates. Stannous chloride ispreferred either anhydrous or hydrated.

Examples of suitable platinum salts are platinic chloride, platinouschloride, platinic bromide, platinous bromide, platinic iodide,platinous iodide, platinic sulfate, platinous nitrate, platinicphosphate and the like. Preferred platinum salts are the alkali metalsalts of haloplatinum acids such as K Ptl3r Li PtCl -6H O,

and the like. Alkali metal salts and especially potassium and sodiumsalts of chloroplatinum acids are more preferred, e.g. KzPtClg, Na PtCl-4H O, K2PtC14, Na PtCl An especially useful catalyst combination isSnCl -2H O and an alkali metal salt of a chloroplatinic acid such asKgPtCle, OI Na PtCl Special preparation of the catalysts does not appearto be required. In general, as set out in US. 2,876,254, the suitablemetal salts are dissolved directly in the alcohol reactant which isbeing used in the carboxylation. Molar ratios of alcohol soluble tin orgermanium salt to haloplatinum acid of from 1:1 to 20:1 can be used inthe preparation of the catalysts. The amount of catalyst which can beemployed can be varied widely, but is generally about 0.0001 to about0.2 mole of contained platinum metal per mole of reactant alcoholcharged into the reactor.

Alkyl ethers when used with an activator amount of water increase therate of the carboxylation reaction. Typical alkyl ethers have from 4 toabout 16 carbon atoms such as morpholine, diethyl ether, 1,4-dioxane,din-butylether, di-n-hexylether, di-Z-ethylhexyl ether, C C dialkylglycol ethers and polyethers such as 1,2-diethoxy ethane, bis[ 2(2methoxyethoxy)ethyl], ether bis(2-butoxy ethyDether, 1,2-dipropoxypropane and the like. Mixtures of the ethers can also be used.

An especially preferred alkyl ether is 1,2-dimethoxy ethane.

As will be illustrated below these alkyl ethers in combination withwater unexpectedly improve the rate of the catalytic carboxylation of Cand higher olefins and preferably C and higher olefins to produceesters.

The amount of alkyl ether used ranges from about 10 percent to about 70percent by weight of the total alcohol/ olefin charge. Generally,percent to about percent by weight of the promoter can be used.

The action of the alkyl ether is not fully understood. Although notbound by any theory, it is thought that the ether may function as acomplexing agent. Whatever the mechanism, the presence of the alkylether and the water unexpectedly improves the overall rate of thecarboxylation reaction.

Water is an essential component in the present process. In other words,essentially no conversion of olefin, that is, no reaction of olefin, COand alkanol to produce ester, will occur in the alkyl ether, Sn or Ge/Pt catalyzed system unless a sufficient amount of water is present. Atleast 10 moles of water per mole of platinum contained in the catalystis needed to activate the system. The process can also be carried out inthe presence of up to moderate amounts of water. Thus, for example, thereaction to produce esters will proceed when the catalyst componentsprovide at least the minimum amount of water as water of hydration (e.g.SnCl -2H O) or when the alcohol reactant contains sufiicient Water andthe like. Excess amounts of water, that is, over about moles of waterper mole of contained platinum, should be avoided. A preferred range ofwater concentration is 16 to 84 moles of water per mole of platinum.

The temperature at which the reaction is carried out may vary over awide range. In general, temperatures in excess of about 30 C. are used.The temperature range of from about 30 C. to about 325 C. may beemployed. Temperatures from about 50 C. to about 275 C. are convenientlyused. Temperatures ranging from about 70 C. to about C. are preferred.The process may be carried out under pressure ranging from 500 to about10,000 pounds per square inch (p.s.i.). Reaction pressures of from about750 to about 5,000 p.s.i. are conveniently used.

The product obtained in the present carboxylation process is a mixtureof ester isomers. This is illustrated by the following reactionequation:

The product obtained thus, is a mixture of linear and branched esters.The major product obtained in the present process is the linear ester.By major product I mean more than about 60 percent by weight of theester mixture is the linear ester.

This mixture of ester isomers may be separated if desired by anysuitable separation methods such as by fractional distillation, byselective absorption, and the like. The mixture of esters may likewisebe used as such without any separation of isomers.

As the examples which follow will show, by using the ether and H 0 therate of the carboxylation reaction is increased substantially. In thefollowing examples, mmoles stands for millimoles.

EXAMPLE 1 Ether; substantially water free A suitable sized autoclave wascharged with 90 mmoles of dodecene-l, 490 mmoles of methanol, about 26grams of 1,2-dimethoxy ethane, 1.0 gram of K PtCl (anhydrous) and 1.9grams of SnCl (anhydrous). Carbon monoxide was introduced into theautoclave to a pressure of 2750 p.s.i. The reaction mass was heated to90 C. with stirring. Carbon monoxide was then added to a total pressureof 3200 p.s.i. The reaction was continued at this temperature for 1hour. During this time a total pressure drop of 25 p.s.i. was recorded.The reaction mass was cooled to room temperature and the autoclave wasvented; 58.3 grams of liquid product was obtained. Analysis of theproduct by vapor phase chromatography showed that no olefin conversionhad occurred.

EXAMPLE 2 Ether; activator water added A suitably sized autoclave wascharged with 90 mmoles of dodecene-l, 485 mmoles of methanol, about 26grams of 1,2-dimethoxy ethane, 1.0 gram of K PtCl (anhydrous), 1.9 gramsof SnCl (anhydrous) and 33 mmoles of water. Carbon monoxide wasintroduced to a pressure of 2750 p.s.i. The reaction mass was heated to3175 p.s.i. The reaction was continued at this temperature for 1 hour, apressure drop of p.s.i. being recorded. The reaction mass was cooled toroom temperature and the autoclave was vented; 60.4 grams of a liquidproduct was obtained. Analysis of this product by vapor phasechromatography showed that the conversion of olefin was 32 percent andthe yield of methyl tridecanoates based on the conversion, was 72percent, of which 86 percent was the linear ester.

The ester products of the present reaction have many uses in thechemical field. For example, the esters may be used as solvents; asplasticizers for resins such as polyvinylchloride, and the like; aschemical intermediates EXAMPLE 3 in ester interchange reactions. Theesters may also be Ether; water to hydration as activator hydrolyzed toyield acids which are useful as detergent intermediates. The tln orgermanium salts used as cata- A sultably SlZed autoclave was chargedWlth 92 mmoles lysts in the present invention are, in general, solublein Of q 423 mmoles of methanol, 289 grams of alchol. Some of the usefulplatinum salts are also soluble 1,2-d1mt110Xy ethane, 1 gram of z s andgrams in alcohol. Soluble in alcohol means soluble in a lower of 2' 2 yf CI1ta 1n$ about 33 mmoles alkanol such as ethanol, methanol,isopropanol and the 0f 2 carbqn mollOXldP Was Introduced to 3 P5 like.Salts of tin or germanium and platinum salts which sure of 2000 p.s.1.The reactlon mass was heated to 90 are not soluble in alcohol but whichare soluble in the and carbfm monoxld? was a total Pressure of olefin,the ether and/or the activator amount of water 3000 P- The reacuon wcontinued for one 15 present can also be used. On the other hand, tin orgermapressure drop of 300 p.s.1. was reco The l'eactlon niurn salts andplatinum salts which are not soluble in mass was cooled to roomtemperature and the autoclave any component of the reaction system canalso be 58 was vented; 64.4 grams of llqllld product Was Obtamed- Inthis case, the combination of tin or germanium salts Analysis of theproduct by vapor phase chromatosraphY and noble metal acids may bedispersed directly in the showed 'f olefin converslon was 72 Percen t-The Yleld of reaction system using methods known in the art; or themethyl tfldecanoates was 98 Percent of whlch 85 Percent catalyst metalsalts and noble metal acids may be used was thslmear ester deposited onan inert support.

The improvement in rate of reaction and the necesslty The process ofthis invention is properly described of activator water is clearlyillustrated by the examples set above The examples presented serve toillustrate, but out g' g 1 i i g g fi g g are not meant to limit thisinvented process. It is intended occurre W en 0 ecenewas ea e or 011r athat this invention be limited only within the scope of C. 1n anautoclave with CO and methanol 1n the presence the following claims. ofrmxed tin/platinum catalyst and an ether. I claim Using the samereactant system and ether promoter as in Example 1, but adding anactivator amount of water 2 25223335 g i zfi g ggggigg i t it 5 (Hzozptmolar ratio of 16:1) 32 percent of the dock (X) at least 05c :1 hicarbor i-to-carbon doub le bond cene-l was converted, i.e., reactedafter one hour at 90 and p C. (Example 2). Thus, in Example 1 there wasessentially no reaction of dodecene-l with methanol and CO using a g ggg iggg f figgg g g g 3 thin/platinum catalyst in the presence of anether. By 30 r an 01 fi i h t t f: t adding a small amount of water tothe same reactants th e 0 mac an o 0 under substantially the sameconditions as in Example 1, m 6 presence 0 32 percent of dodecene-lreacted to produce methyl tri- (a) from 0-0001 to mole of contained Plan'decanoates (Example 1). Example 3 shows that providnum metalrer, moleof P 9 reactant of a ing the water as water of hydration (SnCl '2H O)causes 40 catalyst Whlch 1S a comblnatlon of 71 percent of thedodecene-l to react. Thus, Examples (1) an alfiohol solubls s 01f ametal Selected 1-3 clearly show that a small amount of Water is required"from tm and germamum to activate the reaction of an olefin, CO andalcohol to Salt p f fit/116ml?! the 5 produce esters in the presence ofan ether. {3110 Of 531d Sald Platlflum m The following table containsdata for a series of ex- 1S ffOm 131t0 2021, and amples of thecarboxylation process in which an ether and (b) from 10% to about byweight, based water are used. In each case, where the analogous reaconthe total olefin/alcohol reactant, of an alkyl tion is run without anactivator amount of water, essenether having from 4 to about .16 carbonatoms, tially no carboxylation occurs or if it does occur, the rate andup to 6 O groups, and is substantially lower. 50 (c) an activator amountof water, said activator TABLE 1 HzO:Pl', 00 Reaction Catalyst (molepressure tempera- Alkyl ether Major ester Olefin (moles) Alcohol (moles)(partszparts) ratio) (p.s.i.) ture C.) (weight percent) product sEthylene (1) Ethanol (1) GeCluHbPtCh (5:1) 10:1 1,500 50 1,2-diprtgg1xypro- Ethyl propionate.

an Pentadecene-l (1) Tert-butanol (2) GeBruHzPtBn (20:1) :1 6,000 85Dim]; ether (40)... Telrt-brtylt 6X3 803.1103 6. Dotriacontene-l (1)n-Hexanol (1.5) GeCluHzPtIa (6:1) 30:1 2,500 150 Digfoamyl ethern-Hexyl-tri-ttrion 1108. 6. Hexadecadiene-1,4 (1)-.- Isopropanol (l0)GeCl4ZH2PtI4 (2:1) 75:1 4,500 75 Tetrahydrofuran lsggropid ihepta-8.1108 9. Nonadecene-l (1) 2-ethyl-n-hexanol (8).. SnClzzHgPtBm (1:1.1)50:1 2,100 Ethyl amyl ether 2-etil1 yl-n-hetxyl 8 0881108 c.Tetracosene-l (1) n-Decanol (6.5) GeChzHzPtClu (2.5:1) 15.1 3,600 1001,2-bis[2-(2-butoxyn-Dfecyl pentaetbhoxwzazthoxy} cosanoate. e 8116Heptadccenc-l (1). Cyclohexanol (4) SnCl2:H2PtBr4 (1:1. 5) 25:1 750 961,2-dtmethoxy Cyelohexyl octaethane (44). decanoate. Octadiene-1,7n-Butanol (3. 5) SnBmHzPtBrt (1:0.1) 45:1 3,000BisIZ-(Z-ethoxydi-n-Butyl eghoxyzggghyl} sebacate.

81 Octadecene-l (1) 2-pentanol (9) SnSO4:H2PtIa (6:1) 86:1 1,000 70 1,3-Dioxane (32) l-methyl-n-butyl nonadecanoate. Pentene-l (1) 4-nonanol(5) SnChzHzPtCh (3:1) 20:1 10,000 82 Bis(2-but0xyethyl)-l-propyl-n-hexyl ether (66). hexanoate.

1 Weight ratio; also either or both catalyst components may be hydratedor non-hydrated.

= Based on total reactant charge. 3 Branched isomers are also producedas illustrated in Equation 1. 4 n.Butyl nonanoate, unsaturated estersare also produced.

amount ranging from at least 10 and not over about 90 moles of water permole of contained platinum in said catalyst.

2. The process of claim 1 wherein said activator amount is from at least10 to 9O moles of water per mole of contained platinum in said catalyst.

3. The process of claim 2 wherein said alcohol reactant is a C -Calkanol.

4. The process of claim 3 wherein said alkanol is a C C monohydroxyprimary alkanol.

5. The process of claim 4 where said alkanol is metha- 1101.

6. The process of claim 1 wherein the molar ratio of olefinzalcoholreactant is from 1:1 to about 1:6.

7. The process of claim 6 wherein said olefinzalcohol molar ratio is 1:2to about 1:6.

8. The process of claim 1 wherein the reaction temperature is from about50 C. to about 275 C. and the reaction pressure is from about 500 toabout 10,000 pounds per square inch.

9. The process of claim 8 wherein said reaction temperature is fromabout 70 C. to about 120 C. and said reaction pressure is from about 750to 5000 pounds per square inch.

10. The process of claim 9 wherein said olefinzalcohol reactant ratio is1:1 to about 1:6 and said alcohol reactant is a C -C alkanol.

11. The process of claim 10 wherein said alkanol is a C -C monohydroxyalkanol.

12. The process of claim 10 wherein said alcohol soluble salt is ahalide of tin or germanium and said salt of platinum is a halide ofplatinum.

13. The process of claim 10 wherein said alcohol soluble salt is a tinor germanium halide and said salt of platinum is an alkali metal salt ofa haloplatinum acid.

14. The process of claim 1 wherein said alcohol soluble salt is ahalogen salt of tin or germanium.

15. The process of claim 14 wherein said alcohol soluble salt is ahalogen salt of tin.

16. The process of claim 13 wherein said platinum salt is a platinumhalide.

17. The process of claim 13 wherein said platinum salt is an alkalimetal salt of a haloplatinum acid.

18. The process of claim 1 wherein said olefin is a monoolefin.

19. The process of claim 18 wherein said alcohol reactant is a C -Calkanol.

20. The process of claim 19 wherein said alcohol 501- uble salt is ahalide of tin or germanium and said platinum salt is a platinum halide.

21. The process of claim 19 wherein said alcohol soluble salt is ahalide of tin or germanium and said platinum salt is an alkali metalsalt of a haloplatinum acid.

22. The process of claim 19 wherein said alkanol is a C -C monohydroxyalkanol and said ether is C -C dialkyl glycol ether.

23. The process of claim 20 wherein said alkanol is a C -C monohydroxyalkanol and said ether is C -C dialkyl glycol ether.

24. The process of claim 21 wherein said ether is 1,2- dimethoxyethaneand said alkanol is methanol.

25. The process of claim 22 wherein said ether is 1,2- dimethoxyethaneand said alkanol is methanol.

26. The process of claim 8 wherein said olefin is (f -C olefin, saidalcohol reactant is C C monohydroxy alkanol, said olefinzalcoholreactant molar ratio is 1:1 to about 1:6, and said alcohol soluble saltis a halide of germanium or tin, and said activator amount of water isat least 10 moles of water per mole of platinum in the catalyst.

27. The process of claim 26 wherein said olefin is an a-monoolefin.

28. The process of claim 26 wherein said platinum salt is selected fromplatinum halides and alkali metal salts of haloplatinum acids.

29. The process of claim 28 wherein said platinum salt is alkali metalsalt of haloplatinum acids.

30. The process of claim 28 wherein said alkanol is a C -C monohydroxyalkanol and said ether is C -C dialkyl glycol ether.

31. The process of claim 30 wherein said alkanol is methanol.

32. The process of claim 31 wherein said ether is 1,2- dimethoxyethane.

33. The process of claim 32 wherein said olefin is dodecane.

References Cited UNITED STATES PATENTS 2,876,254 3/ 1959 Jenner et al.260-486 2,916,513 12/ 1959 Lautenschlager et al. 260-486 2,962,52511/1960 Johnson et al. 260--486 LEWIS GOTTS, Primary Examiner D. G.RIVERS, Assistant Examiner US. Cl. X.R.

260-408, 410, 410.5, 468 CB, 479 R, 485 R, 486 AC, 497 A

